>
>
>Richard wrote:
>
>> >Definitely not multi band or even multi frequency. Single frequency only.
>> >From what I understand they were a real pain to keep tuned properly.
>>
>> I heard the same thing.
>>
>> >Advantage was high level modulation and class C efficiency without the
usual
>> >big high level modulator.
>> >
>> A Class AB1grid-driven, or AB2 g-g linear amplifier is typically 60%
>> efficient. Class C may be 78% efficient but the difference would be
>> virtually not noticeable at the Rx end or on the utilities bill.
>>
>> cheers, Gary
>
>With AM though the carrier efficiency is only about 30% with a linear amp.
True. When I run AM, I use VOX so there is minimal carrier time. Whilst
talking, the efficiency is better. For better efficiency I run DSB and
SSB. The trouble with most AMers is that they like to take 10-minute
turns in rotation, so they find VOX affrontive. Imagine a guest coming
into your home and taking a 10-minute transmission while you keep your
mouth in Rx mode.
>
>The amp needs to be tuned at and able to handle 4 times the carrier power to
>handle the audio peaks for 100% modulation.
Correctamundo. This is easily accomplished by sending dits at max pep,
tuning the amp for max pep out, and lastly adjusting the AM carrier
control for 25% of max pep.
> Most stations run upwards of 120% positive
>peak modulation making the amp PEP power handling requirement even greater
>than 4 times carrier.
I get clean sounding AM with a 4 to 1 ratio or with c. a 10,000 to 1
ratio -- a.k.a., DSB.
>Efficiency will be even less in that case. Lots of heat to
>get any kind of real power on AM with a linear amp.
>
Which is a good reason to use SSB and VOX.
cheers, Gary
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
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